A piezoelectric actuator made of piezoelectric material typically responds quickly and thus can be controlled precisely. One of the applications of such a piezoelectric actuator is a fine motion mechanism for producing fine movement of an object at high speed in a plane (see Patent literature 1, for example). In order to construct such a fine motion mechanism, a piezoelectric actuator 600 shown in FIG. 22, for example, is used. The piezoelectric actuator 600 includes a piezoelectric layer 400 made of platelike piezoelectric material polarized in the direction of thickness (in the Z-axis direction shown in FIG. 22), a first electrode layer 401 formed on one of the thickness-wise faces of the piezoelectric layer 400, and a second electrode layer 402 formed on the other thickness-wise face of the piezoelectric layer 400. The first electrode layer 401 is divided into two individual electrodes 401a and 401b, which are side by side in the direction of width of the piezoelectric layer 400 (in the X-axis direction) and extend in the direction of length of the piezoelectric layer 400 (in the Y-axis direction). When voltages are applied to the piezoelectric layer 400 through the first and second electrode layers 401 and 402, electric fields are applied to the piezoelectric layer 400. At this time, the voltages are applied so that the electric filed 403a (downward in FIG. 22) between the one individual electrode 401a of the first electrode layer and the second electrode layer 402, and the electric filed 403b (upward in FIG. 22) between the other individual electrode 401b of the first electrode layer and the second electrode layer 402 are the same in magnitude but opposite in direction. Consequently, when one side of the piezoelectric layer 400 in the with direction thereof expands in the length direction, the other side contracts in the length direction, whereby with respect to one of the lengthwise ends of the piezoelectric layer 400, the other end is displaced in the width direction (to the contracting side) of the piezoelectric layer 400.
FIG. 23 illustrates a fine motion mechanism constructed using the piezoelectric actuator 600 described above. More specifically, one of the lengthwise end portions of the piezoelectric layer 400 of the piezoelectric actuator 600 is secured to a fixed member 601, while to the other end portion, a movable member 602 is fixed, thereby forming the fine motion mechanism. In this fine motion mechanism, voltages such as mentioned above are applied to the two individual electrodes 401a and 401b to drive the piezoelectric actuator 600, whereby the movable member 602 can be moved slightly in a certain plane with respect to the fixed member 601 in the width direction of the piezoelectric layer 400.
A fine motion mechanism such as described above is used in, e.g., a camera module equipped with an imaging device 500 and an optical lens 501 as shown in FIG. 24, so as to move the imaging device 500 relatively to the optical lens 501 in a plane perpendicular to the optical axis 0 of the optical lens 501, thereby performing a technique (so-called pixel-shifting) in which an image having a higher resolution than that of the imaging device is obtained (see Patent literature 2, for example). In FIG. 24, the reference numeral 502 refers to a holder serving as a movable member for holding the imaging device; 503 to an piezoelectric actuator for moving the holder 502 (the imaging device) in the Y-axis direction in FIG. 24; and 504 to a piezoelectric actuator for moving the holder 502 (the imaging device) in a direction perpendicular to the paper of FIG. 24.
The fine motion mechanism described above is also applicable to a hand-shake-caused-blurring correction mechanism in a camera shown in Patent literature 3. In this hand-shake-caused-blurring correction mechanism, the fine motion mechanism moves the imaging device, the optical lens, and the like so as to cancel hand-shake detected by an angular velocity sensor.    [Patent literature 1] Japanese Laid-Open Publication No. 2001-339967    [Patent literature 2] Japanese Laid-Open Publication No. 2004-96673    [Patent literature 3] Japanese Laid-Open Publication No. 2004-348147